Cervical secretory immunoglobulin A to human papillomavirus type 16 (HPV16) from HPV16-infected women inhibit HPV16 virus-like particles-induced hemagglutination of mouse red blood cells

Broadly neutralizing antibodies for HIV prevention: a comprehensive review and future perspectives

SUMMARYThe human immunodeficiency virus (HIV) epidemic remains a formidable global health concern, with 39 million people living with the virus and 1.3 million new infections reported in 2022. Despite anti-retroviral therapy's effectiveness in pre-exposure prophylaxis, its global adoption is limited. Broadly neutralizing antibodies (bNAbs) offer an alternative strategy for HIV prevention through passive immunization. Historically, passive immunization has been efficacious in the treatment of various diseases ranging from oncology to infectious diseases. Early clinical trials suggest bNAbs are safe, tolerable, and capable of reducing HIV RNA levels. Although challenges such as bNAb resistance have been noted in phase I trials, ongoing research aims to assess the additive or synergistic benefits of combining multiple bNAbs. Researchers are exploring bispecific and trispecific antibodies, and fragment crystallizable region modifications to augment antibody efficacy and half-life. Moreover, the potential of other antibody isotypes like IgG3 and IgA is under investigation. While promising, the application of bNAbs faces economic and logistical barriers. High manufacturing costs, particularly in resource-limited settings, and logistical challenges like cold-chain requirements pose obstacles. Preliminary studies suggest cost-effectiveness, although this is contingent on various factors like efficacy and distribution. Technological advancements and strategic partnerships may mitigate some challenges, but issues like molecular aggregation remain. The World Health Organization has provided preferred product characteristics for bNAbs, focusing on optimizing their efficacy, safety, and accessibility. The integration of bNAbs in HIV prophylaxis necessitates a multi-faceted approach, considering economic, logistical, and scientific variables. This review comprehensively covers the historical context, current advancements, and future avenues of bNAbs in HIV prevention.

Use of broadly neutralizing antibodies for HIV-1 prevention

Antibodies have a long history in antiviral therapy, but until recently, they have not been actively pursued for HIV-1 due to modest potency and breadth of early human monoclonal antibodies (MAbs) and perceived insurmountable technical, financial, and logistical hurdles. Recent advances in the identification and characterization of MAbs with the ability to potently neutralize diverse HIV-1 isolates have reinvigorated discussion and testing of these products in humans, since new broadly neutralizing MAbs (bnMAbs) are more likely to be effective against worldwide strains of HIV-1. In animal models, there is abundant evidence that bnMAbs can block infection in a dose-dependent manner, and the more potent bnMAbs will allow clinical testing at infusion doses that are practically achievable. Moreover, recent advances in antibody engineering are providing further improvements in MAb potency, breadth, and half-life. This review summarizes the current state of the field of bnMAb protection in animal models as well as a review of variables that are critical for antiviral activity. Several bnMAbs are currently in clinical testing, and we offer perspectives on their use as pre-exposure prophylaxis (PrEP), potential benefits beyond sterilizing immunity, and a discussion of future approaches to engineer novel molecules.

Neutralization of HIV by milk expressed antibody

BACKGROUND

In some areas of the world, mother-to-child transmission of HIV remains a significant problem in part due to widespread breastfeeding, which is essential because of scarce supply of a safe replacement, protection conferred by breast milk against many enteric illnesses, and cultural norms. We propose that sustained adequate levels of protective antibodies in breast milk will prevent transmission of HIV.

METHODS

The HIV-neutralizing human monoclonal antibody b12 (IgG1) has been expressed as an IgA2 in CHO cells and shown to retain full immunoreactivity and neutralizing activity as the parental IgG1. The expression plasmids containing the b12 heavy and light chains were also used to construct milk-specific expression vectors using the GTC goat β-casein expression vector to direct expression of linked genes to the mammary gland with subsequent secretion into the milk. Female transgenic mice were generated and following parturition, their milk was tested for antibody immunoreactivity with gp120 and neutralization of HIV.

RESULTS

When milk-derived b12 IgA2 was compared with CHO-derived b12 IgA2 (or IgG1), immunoreactivity was retained. When tested for neutralization, milk-derived b12 IgA2 was at least comparable to CHO-derived antibody and in some cases, superior to CHO-derived antibody. Furthermore, milk that expressed b12 IgA2 was significantly more effective at mediating antibody-dependent cell killing.

CONCLUSIONS

These results suggest that it is possible to achieve functional HIV-specific mAb in the milk of transgenic mice, and further investigations are warranted to explore ways for inducing this type of antibody response in the breast milk of HIV-infected women.

Structural Requirements for the Interaction of Human IgA with the Human Polymeric Ig Receptor

Transport of polymeric IgA onto mucosal surfaces to become secretory IgA is mediated by the polymeric Ig receptor (pIgR). To study the interaction of human dimeric IgA (dIgA) (the predominant form of IgA polymer) with the human pIgR (hpIgR), we generated recombinant wild-type dIgA1 and dIgA2m(1) and various mutant dIgA1 and analyzed their interaction with a recombinant human secretory component and membrane-expressed hpIgR. We found that wild-type dIgA1 and dIgA2m(1) bound to recombinant human secretory component with similar affinity and were transcytosed by the hpIgR to the same extent. Mutation of the IgA Calpha2 domain residue Cys311 to Ser reduced binding to hpIgR, possibly through disruption of noncovalent interactions between the Calpha2 domain and domain 5 of the receptor. Within the Calpha3 domain of IgA1, we found that combined mutation of residues Phe411, Val413, and Thr414, which lie close to residues previously implicated in hpIgR binding, abolished interaction with the receptor. Mutation of residue Lys377, located very close to this same region, perturbed receptor interaction. In addition, 4 aa (Pro440-Phe443), which lie on a loop at the domain interface and form part of the binding site for human FcalphaRI, appear to contribute to hpIgR binding. Lastly, use of a monomeric IgA1 mutant lacking the tailpiece revealed that the tailpiece does not occlude hpIgR-binding residues in IgA1 monomers. This directed mutagenesis approach has thus identified motifs lying principally across the upper surface of the Calpha3 domain (i.e., that closest to Calpha2) critical for human pIgR binding and transcytosis.

Immune responses to human papillomavirus in genital tract of women with cervical cancer

OBJECTIVES

To address a question whether immune responses to HPV infection play a role in control of cervical cancer, we analyzed systemic and mucosal immune responses to HPV in women who underwent radical hysterectomy for cervical cancer (HCC) or loop conization due to cervical dysplasia (LOOP), or had hysterectomy for other reasons (HNN).

METHODS

HPV-specific antibodies in sera and vaginal washes were determined by ELISA using recombinant HPV 16 E7 oncoprotein. Cytokines in vaginal washes were assayed by Linco cytokine multiplex method using Luminex technology. Differential gene expression profiling in cervical tumor was determined by microarray analysis and Real-time RT-PCR.

RESULTS

While levels of HPV-16 E7-specific IgG in vaginal wash were significantly higher in women undergoing HCC and HNN, the levels of the HPV-16 E7-specific IgA in vaginal wash of women with cervical cancer and cervical dysplasia were lower as compared to patients in HNN. Proinflammatory cytokines, such as IL-6 and IL-8, were dominant in vaginal washes of all subjects studied. However, no pattern of Th1-type and Th2-type cytokine induction was observed as demonstrated by protein analysis as well as differential gene expression profiling in cervical tumor.

CONCLUSIONS

These results suggest a selective down-regulation of local HPV-specific IgA responses in women with cervical cancer.

Identification of peptide sequences specific for serum antibodies from human papillomavirus-infected patients using phage display libraries

Three random phage display peptide libraries were screened with sera from human papillomavirus (HPV)-infected patients to characterize the specificities of antibodies present in patients' sera and to identify molecules that correspond to or mimic natural epitopes; 141 phage clones were randomly selected in three rounds of bioselection and their binding properties were analyzed in ELISA using sera from 36 patients with confirmed HPV 16 infection and 24 healthy control female blood donors. Sixteen of 36 (44%) patients' sera reacted with at least 1 phage clone, and only 2 of 24 female donors' sera showed positive reaction with 1 of the selected clones. We conclude that the combination of various disease-specific epitopes generated by screening of phage display peptide libraries may potentially lead to a multicomponent diagnostic assay for the early detection of HPV infection and precancerous cervical lesions, making possible the prevention of one of the most common cancers in women.